Electrical connecting device



Nov. 13, 1956 E. HOFMANN 2,770,794

ELECTRICAL CONNECTING DEVICE Filed Dec. 1. 1949 other by screwing or the like.

United States Patent 2,770,794 ELECTRICAL CONNECTING DEVICE I Erich Hofmann, Dusseldorf, Germany Application December 1, 1949 Serial No. 130,449 Claims priority, application Switzerland Marcl130, 1949 Claims. (or. 339- 273 It is known to use as an electrical connecting appliance a clamping device which is constituted by an outer casing enclosing a metal socket comprising two frusto-conical halves. Two clamping elements such as balls are arranged in said socket, so as to be slidable longitudinally with respect thereto and so urged towards the terminal smaller cross-sections of said socket by a compression spring interposed between them, that the conducting wires introduced on either side between each ball and the corresponding wall of the metal socket is firmly squeezed. Such a clamping device thus permits to establish a simple electrical connection between two conducting wire ends, said connection being very easily established, while being nevertheless very safe.

Since the manufacture in one piece of such a biconic clamping device has given rise heretofore to great difficulties, the two truncated cones of the metal socket are usually assembled by their large bases in contact with each However, even with most carefully assembled metal sockets, it has been difiicult to avoid drawbacks resulting from the fact that the conductor resistance at the assembling place does not correspond to that of the other parts of the socket and from the fact that the assembling connection itself tends to yield and to become faulty. It results from said drawbacks not only undesired beatings and current losses, but also current breaks, when, due to any permanent or intermittent vibrations, the assembling connection between the two parts is released and becomes unsafe (loose contact).

This invention has for its object a biconic metal socket of this type constituting the inner part of a clamping device made, e. g. of a molded material so constructed that its two halves offer an uninterrupted metallic and hence electric connection. The socket thus obtained is then coated in a manner known per se, with an outer casing made of a suitable insulating material, such as synthetic resin molded material.

The invention will be better understood with reference to the accompanying drawings in which illustrative embodiments are shown.

In these drawings:

Fig. 1 is a cross-sectional view of a clamping device according to the invention,

Figs. 2 to 4 are diagrammatical views of four constructive embodiments of the inner biconic socket ofiering an uninterrupted metallic and hence electric connection.

Figs. 5 and 5a are, respectively, a plan view and perspective view of a single socket and plug combination, at an intermediate stage of manufacture.

The clamping device according to the invention is constitu-tcd by a metal socket 1, the frusto-conical halves of which are in contact with each other by their larger base and offer an uninterrupted metallic and electric connection. The socket is outwardly coated, e. g. with an insulating molded material 4. The two ends of a spiral coil spring 5 urge two clamping elements 6 and 7 towards the small conical cross-sections of the inner socket thus squeezing the two wire ends 8 and 9 safely and firmly.

2,770,794 Patented Nov. 13, 1956 2 According to the main feature of the invention, the two cones 2 and 3 of the metal socket 1 should be inter-' connected through an uninterrupted metallic and hence electric connection, i. e. a connection which is not obtained by' means of screws, soldering or the like but, on

the contrary, through the metal proper. This may be provided by means of several embodiments:

In the example shown in Figs. 2 and2a, two metal plates 10, 11 having the same size and shape which are integrally interconnected through a lug 12 are drawninto two conic horns 13 and 14 which remain interconnected through said lug 12. It is then only necessary to bring said metal horns into contact by their larger base by bending them about the mid-axis of lug 12 which is grooved for this purpose to obtain directly the metal inner socket 1 around which the molded material is then compressed.-

bending said, halves about the longitudinal axis of said lug into the desired socket. In this case also, the insulating material is deposited around said socket subsequently, after having assembled the halves 15, 16.

Another mode of construction is shown in Fig. 4. In this case, the socket 1 is constituted by a lower frustoconical part '17 and an upper part 18 provided with slots. Said slots are so disposed that said upper part 18 of the socket also assumes a frusto-conical shape after the tongues have been brought together.

The clamping device shown in Fig. l is used for connecting electrically two wire ends. It is however also possible to manufacture by the same principle usual plug connecting devices. In this case, it is only necessary to use one of the frusto-conical halves e. g. 2, a plug being substituted for the other frusto-conical half 3. But, in this case also, it is required that the metal truncated cone is connected to the plug through an uninterrupted connection which is perfectly safe and constant.

Figs. 5 and 5a show how such a connection may be effected according to the invention. The frusto-conical metal socket 21 is drawn from one of two metal plates 19, 20 interconnected as previously through a lug 12", while the plug 23 is secured in the opening 22 of the unchanged plate 20, e. g. by welding, soldering or the like.

The above described method permits to manufacture in any case biconic metal sockets, the truncated cones of which offer an uninterrupted metallic connection. This is an essential condition for obtaining known clamping devices having good properties. In order to obtain also a contact as safe as possible between the wires to be interconnected and the metal socket, it is possible to provide in the inner wall of the metal socket, one or more longitudinal grooves.

It will be understood that the invention is in no way limited to the above described embodiments in which many modifications may be made within the scope of the invention.

What I claim is:

1. A clamping connection device adapted to be interposed between the ends of two electric conductors to be interconnected, comprising a metal socket formed of a shell having the shape of a truncated cone provided with an outer insulating material casing, an integral clamping element having a peripheral surface of revolution having a diameter larger than the smallest internal diameter of said cone at the apex of said cone and smaller than the smaller end thereof of said socket and adapted tddirec'fly contact and squeeze one of said conductor ends against the inner conical wall of said socket, so as to establish direct electric contact therebetween, elastic resilient means located within the socket and adapted to urge said clamping element toward the smaller end of said cone into its squeezing position to provide firm direct contact between the conductor and the conical wall surface irrespective of the smallness of the conductor diameter, and conductive means formed'integrally with said socket and adapted for contact with a second electric conductor, sothat there is provided between said electric contacts an integral uninterrupted metallic electric path.

2. A'device according to claim 1 in which said conductive means is in the shape of a second truncated cone complementary to said first named cone and enclosed within the same insulating casing with its larger end abutting the larger end of said first named cone, and which includes a second spherical clamping element having a diameter larger than the smallest internal diameter of said second cone and smaller than the largest internal diameter thereof, disposed within said second cone adjacent the smaller end thereof, and in which said elastic means extends into both said cones and urges both said clamping elements into conductor-holding position.

3. A device according to claim 2 in which said cones are seamless and are integrally connected by a lug extending between their abutting larger ends.

4. A device according to claim 2 in which at leastone of said cones is split lengthwise along at least two lines.

5. A device according to'claim 1 in which said conductive means is in the form of a plate adapted for attachment to a plug.

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